Apparatus for combining cellular telephone ring signals and PSTN ring signals

ABSTRACT

A ring detection device which signals a modem in a personal communication device. A detector is connected to the cellular radio telephone for detecting an incoming telephone call. An oscillator circuit generates a ringing signal for enabling a modem in response to either the cellular telephone incoming call or a ring signal received over a directly-connected PSTN network. The modem for the personal communication device responds for providing communication over either the cellular network or directly-connected PSTN network.

The application is a continuation of application Ser. No. 08/279,659filed on Jul. 25, 1994, now abandoned.

RELATED APPLICATIONS

This application is related to the following patent applications:

Application Ser. No. 08/310,728; Attorney Docket No. BC994-050;

Application Ser. No. 08/279,640; Attorney Docket No. BC994-096;

Application Ser. No. 08/279,644; Attorney Docket No. BC994-099;

Application Ser. No. 08/279,413; Attorney Docket No. BC994-097; and

Application Ser. No. 08/279,652; Attorney Docket No. BC994-098.

1. Field of the Invention

The present invention relates to personal communication devices whichcommunicate over both cellular radio networks and public switchednetworks (PSTN). More particularly, application Ser. No. 08/146,342 theinvention provides a modem which responds to incoming cellular telephonecalls and incoming ringing signals received from the PSTN network.

2. Background of the Invention

Cellular radio service is now widespread throughout most of the UnitedStates. Standards have been promulgated to permit universal access tothe cellular telephone network by portable telephones and mobiletelephones. The communication protocol standard used in the cellularnetwork is identified as the AMPS protocol. The service permits radiotelephone communication between portable/mobile units, and the publicswitched telephone network (PSTN) through a radio interface.

The cellular service is now digitized and permits not only digitaltelephone traffic but data services as well. Thus, various serviceswhich have been implemented in the PSTN network, such as E-MAIL andfacsimile, may now be implemented as well over the cellular telephonenetwork. A radio modem is implemented at each personal communicationdevice which provides the capability of transmitting and receiving data.

The personal communication devices are often implemented to work througha direct connection to the PSTN network, as well as over the cellularradio network. These devices include an RJ11 jack which connectsdirectly to the PSTN network where available. The problem of having thepersonal communication device respond not only to signalling from thecellular radio network, but also the incompatible signalling from thePSTN network needs to be addressed. Specifically, the modem of thepersonal communication device requires that a ringing signal be detectedin order to initialize the modem for data reception over the cellularradio network, as well as the directly-connected PSTN network. The factthat the cellular radio produces a ringing signal in a different formatfrom the ringing signal produced by the PSTN network makes it necessaryto combine the different ringing signals into a single ringing signalfor initializing the modem.

In view of these difficulties, the present invention has been provided.

SUMMARY OF THE INVENTION

It is an object of this invention to provide in a personalcommunications device a common ringing signal to a modem from either acellular telephone and directly connected PSTN network.

In carrying out the invention, a common ring signal is derived for thepersonal communications device modem. The common ring signal willprovide a signal in the PSTN ring signal format to the modem in responseto a ring signal received over the directly-connected PSTN network orfrom a cellular telephone system ring indication or a command indicatingthat a call has been received over the cellular network. In either case,the modem is initialized in response to the derived ring indicate signaland posts an interrupt to the personal communications system processor.The processor can then enter the cellular radio telephone datareception/transmission mode, if the cellular radio indicates an incomingcall has been received. If no cellular network call has been received,the system defaults to the PSTN network for data transmission andreception.

DESCRIPTION OF THE FIGURES

FIG. 1A is a plan view of a personal communication device employing apreferred embodiment of the present invention.

FIG. 1B is an end view of the personal communication device of FIG. 1A.

FIG. 2 is a block diagram of the device of FIGS. 1A and 1B illustratingthe personal communication device of the preferred embodiment of theinvention.

FIG. 3 illustrates a circuit for generating a common ring signal to themodem of FIG. 2 from either a PSTN ring indicate signal or a cellulartelephone ring signal.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, there is shown a personal communication device10. The personal communication device includes a cellular telephone andan internal data processing system for implementing, via cellular radio,multiple data communication features, such as E-MAIL, facsimiletransmission/reception, etc. The personal communicator 10 includes ahousing 12 which has pushbuttons 14, 16 and 18 mounted along lateralsides thereof. Manual pushbuttons 14, 16 and 18 provide for on/off, up(increase) and down (decrease) functions.

The personal communication device 10 includes a speaker 22 andmicrophone 24 positioned at approximately the standard telephone handsetpositions. In use, the cellular telephone communicates through antenna20 to provide normal two-way voice communication between the user and abase station connected to the PSTN network.

Input/output functions to the processor within the personalcommunications device 10 are effected through the touch-sensitive screen28, and underlying touch screen display 26. The touch screen display 26displays various menus familiar to computer users, and various selectionicons. By using a small pointed stylus 23, it is possible to selectamong menu selections appearing on the touch screen display 26 bypressing stylus 23 against the portion of the touch-sensitive screen 28overlaying the display 26.

The touch-sensitive overlay which identifies user selections made withthe stylus 23, encodes the selection and is read by the processorresident within personal communication device 10.

Various functions such as increased volume, decreased volume, increasedbrightness, decreased brightness, etc. may be implemented by selectingthe appropriate menu function from touch screen display 26 and thenoperating one of switches 16 or 18.

The personal communicating device of FIG. 1A also includes a standardRJ11 jack 25 as shown in FIG. 1B. The personal communication device canbe directly coupled to the PSTN network through a standard telephonycable in those circumstances where cellular radio is not needed.

The protocols used in cellular radio for placing a call and answering acall are set forth in the AMPS standards. These protocol functions arecarried out in a different format, suitable for RF communicationsdifferent from the signalling used in the PSTN network for the samefunctions. The personal communication device of FIGS. 1A and 1Btherefore includes interface circuitry peculiar to the cellulartelephone network protocols and the PSTN network protocols so thatcommunication through both networks is possible.

A block diagram of the electronic circuitry architecture for thepersonal communication device of FIG. 1A is shown in FIG. 2. Referringnow to FIG. 2, a CPU 32 is shown which controls the display of varioususer menus on the touch-screen display 26, as well as provides aninterface between the cellular radio 50 and modem 35.

The system of FIG. 2 operates from programming information contained inEPROM 36, EPROM 38 and RAM 34. RAM 34 stores the application programs,such as the one for the address book/auto dialer, one for placing a callover the cellular radio 50, etc. The system implementation emulates thatof a PC/XT class portable computer. The CPU 32 belongs to the type ofModel VG 230, commercially available from VADEM, Inc., San Jose, Calif.The CPU 32 and its companion controller include an LCD controller 40, acommunications port and various power and bus connections to the bus 33.

The EPROM 36 stores the basic input/output system (BIOS), as well as aself-test program. EPROM 38 contains files for providing a navigatorprogram, the DOS and certain application programs which produce thecommunication and data processing functions, as well as interrupthandling for the CPU 32. Further details relating to this architecturecan be found in U.S. patent application Ser. No. 08/146,342 (AttorneyDocket No. BC993-079, common assignee).

The operation of the touch-screen display 26 and touch screen overlay 28is controlled from a touch-screen controller 40. A screen driver 48provides the illuminating voltages and character drive signals to thetouch screen display 26. The touch-sensitive screen 28 comprises anarray which will sense a force applied to a particular part of the touchoverlay 28 and encode the same as position information. Touch screencontroller 40, via the bus 33, can provide a command identifying thelocation touched on the touch-sensitive screen 28 to the CPU 32. CPU 32can then invoke the selected application program or subroutine of anapplication program stored in the RAM 34 for execution.

A tone generator 44 is shown which will produce an audible beep in thespeaker 22 each time the screen is touched by the user using the stylus23 and a command is successfully decoded. Thus, the user can audiblydetect when his selection has been recognized.

The integrated cellular and PSTN interface is connected to the antenna22 for transmitting and receiving to the local cellular network. Thecellular telephone 50 produces a cellular ring signal indicating that anincoming call is being received by the cellular radio 50. Further, theDAA interface 39 provides a standard PSTN ring voltage from the RJ11connector 25 tip and ring connections. A common ring generator 41receives the ring voltage from the DAA interface 39 and cellular radio50 and produces a single PSTN mode ring signal for modem 35.

In this way, modem 35 is initialized with a PSTN type of ring indicatesignal whether the incoming call is received via cellular radio 50 orover the PSTN RJ11 jack 25. The modem 35 responds to the PSTN ringsignal by posting an interrupt to the CPU 32 which invokes the routinefor communicating by modem. Incoming data from either the PSTN networkor cellular radio 50 is received by the modem 35 as standard modemsignalling tones and processed in the usual way. Further, data is outputfrom the modem 35 to both the cellular radio 50 and interface 39providing communication through either medium.

The capability of providing data communication through either the RJ11jack 25 or cellular radio 50 must take into account different formats ofthe cellular radio network and PSTN network. When placing a call overthe cellular radio network 50, the cellular radio 50 invokes the AMPSprotocol application for sending dial digits via the radio interface toa base station.

The standard for placing calls on the PSTN network uses DTMF tonescorresponding to called number digits. DTMF tones are also used toaccess equipment connected to the called party's telephone, such asbanking information, voice mail messages, etc.

The personal communication device of FIGS. 1A, 1B and 2 receivesincoming calls for data services through either the cellular radio 50 orRJ11 25 connector. The two network services have different ring signalformats. The PSTN network produces a tone of a prescribed frequency andcadence as a ringing signal which is sensed by connected telephoneequipment as an incoming telephone call. The ring signal signals thetelephone equipment to go off hook and signal back via the tip and ringconnections of the RJ11 connector 25 to begin a session with a callingparty.

The cellular telephone ring signal 50 is usually a series of pulsedtones which alert the operator to the incoming phone call. As soon asthe cellular telephone 50 goes off hook, a signal in accordance with theAMPS format is returned to the base station to begin a session via thecellular telephone.

A ring generator 41 of FIG. 2 receives both the PSTN-originated ringsignal and cellular telephone ring signal. The ring generator 41 isshown more completely in FIG. 3. The ring generator 41 accepts acellular telephone ring signal which may be a series of tone pulses orit may be a digital command, depending on the configuration employed inthe cellular telephone controller 50. In the current embodiment, it isassumed that the cellular system ring signal is a series of tone pulseswhich are detected in a tone detector 62. Tone detector 62 provides a DCoutput when the pulse ring signal is detected having a given amplitudeand frequency.

The cellular tone detector 62 provides a signal to gate 63. A PSTN tonegenerator for generating pulses in the PSTN format are supplied fromgenerator 64 to gate 63. Thus, once an incoming cellular telephone callis detected, pulses in accordance with the PSTN ring format are appliedto a Schmit trigger 65. Schmit trigger 65 will produce the required PSTNring signal for triggering modem 35 to go off hook. Modem 35, afterreceiving the ring signal, will initiate an INTERRUPT to CPU 32 to begina communication session. CPU 32 has also been alerted of the incomingcall from a command received from the cellular telephone 50. Thecombination of the modem initiated interrupt and cellular telephoneinitiated receive command is used by CPU 32 to initialize the system fora data service.

Modem 35 will then receive data from the cellular telephone as asequence of tones, and decode the tones into digital data. Digital dataobtained from decoding the tones are available for transfer on bus 33 tothe CPU 32. CPU 32 will forward text for display on the touch screendisplay 26 based on the digital data.

The ring generator 41 also receives a ring signal from DAA interface 39.As is known to those skilled in the art, DAA interface 39 will present aring signal when the ring voltage is detected on the PSTN network to thering generator 41. As the tone and cadence of the ring signal is in theproper format for recognition by modem 35, the signal is coupled viadiode 68 to the Schmidt trigger 65. Schmidt trigger inverter 25 producessharply-defined pulses from the PSTN ring signal. The modem 35recognizes the coupled signal and posts an INTERRUPT as in the casewhere cellular telephone 50 initiates a ring command. The CPU 32 iscapable of determining whether or not the incoming ring signal came froma connected PSTN network through RJ11 connector 25, or via the cellulartelephone network. Modem 35 in either case transfers data to theappropriate interface to engage in a data session with a calling party.

Thus, it is clear that the personal communications device of FIGS. 1A,1B and 2 is capable of data services on either a transmit or receivemode using either cellular telephone communications or standardtelephone line modem communication. Those skilled in the art willrecognize yet other embodiments of the invention described moreparticularly by the claims which follow.

What is claimed is:
 1. A ring detection device for signaling a modemadapted to respond to a PSTN ring signal in a personal communicationdevice which alternatively communicates by radio telephone and through adirect connection to a PSTN that applies a ring signal to indicate anincoming call, said ring detection device comprising:a detectorconnected to said radio telephone for detecting a signal indicating anincoming call and, responsively, producing a call detection signal; anoscillator circuit for generating a simulated ring signal; a gatecircuit connected to receive the call detection signal from saiddetector and the simulated ring signal from said oscillator and passingsuch ring signal to output only in response to a call detection signal;coupling means for receiving ring signals from said PSTN network and asoutput from said gate circuit and applying them to said modem to signalan incoming call whereby said modem is prepared to respond to the call.2. The ring detection device of claim 1 wherein said coupling meanscomprises a Schmidt trigger circuit connected to receive the output ofsaid gate circuit and coupled by a diode to said PSTN network, saidSchmidt trigger circuit passing signals from said gate circuit and saiddiode to said modem.
 3. The ring detection device of claim 1, whereinsaid radio telephone presents a pulsed sinusoidal voltage to indicate anincoming call and said detector includes a filter for selectivelypassing said pulsed sinusoidal voltage.
 4. The ring detection device ofclaim 1, wherein said coupling means converts each received ring signalto a level shifted ring signal.